You have a protein that is well behaved at pH=7.0 (The ph of the buffer is 7.) and the pI of your protein is equal to 4.3 (pI=4.3). You have decided to use ion exchange chromatography to help isolate your protein. 
1.	Using this information, would you use a cationic column (anion exchange) or an anionic column (cation exchange)? Why?
2.	What residues in your protein do you think would be in a majority?
3.	Same question as in question 1 with the exception that your protein has a pI=9.2.